Space cooling system



,/Aug. 428, 195.6 J. E. wooDS 2,760,345

SPACE COOLING SYSTEM Filed Nov. 26, 1952 2 Sheets-Sheet 1 w l r fini/rr PRESSURE REGULATINO 4VALVE INVENToR. `JOHN E, WOODS BY Il,

'rl' l l ATTORNEYS Fig.

Aug. .28, 1956 J. E. wooDs 2,760,345

` SPACE COOLING SYSTEM Filed Nov. 26. 1952 2 Sheets-Shea?I 2 INVENTOR. JOHN E. WOODS ATTORNEYS l BY United States SPACE CDOLNG SYSTEM John E. Woods, Cohasset, Mass., assigner to Standard- Thornson Corporation, Boston, Mass., a corporation of Delaware Application November 26, 1952, Serial No. 322,676

9 Claims. (Cl. 622) The present invention relates to space cooling systems, and more particularly to improvements in a system in which the coolant is in the form of a brine, remaining continuously in the liquid state, and solid carbon dioxide or Dry Ice is used both to extract heat from the coolant and to provide the circulating pressure. The basic system is described in a patent to Brunsing No. 2,450,713.

ln my copending application, Serial No. 120,314, led October 8, 1949, now Patent No. 2,636,357, granted April 28, 1953, i have described certain improvements in the basic Brunsing system, and in my Patent No. 2,608,832, l have described other improvements. The present invention relates to improvements in the invention of my above-mentioned copending application, and includes novel structures and arrangements of parts especially adapted to carry out the objects thereof. A-s hereinafter indicated, the teachings of my above-mentioned Patent No. 2,608,832 may or may not be employed in the practice of the present invention, according to need.

The patent to Brunsing and my above-mentioned application describe the basic circulating system which is empioyed. According to this system, Dry Ice in a suitable form, such as blocks, is placed in two containers, one of which is provided with cooling tubes for extracting heat from the coolant as it is pumped therethrough and into the space cooling tubes, and the other of which generates the carbon dioxide pressure which is applied to the coolant to circulate it through the system. It was pointed out in my above-mentioned application that the success of a system of this type depends to a considerable extent upon the control of the rate of sublimation of the Dry Ice in the container used for generating the pressure. This is a function of the net heat absorbed into this container, hereinafter referred to as the generator, and therefore depends upon the position of the generator relative to the other parts of the apparatus, the properties of the insulation surrounding the generator, and the ternperatures of the surrounding parts.

in the apparatus described in my above-mentioned application, a certain amount of heat escapes from the pressure generator into the other container or Dry Ice bunker where heat is extracted from the coolant. At the saine time, a certain amount of heat is absorbed by the pressure generator from the reservoir in which the returned coolant is stored prior to recirculation. lt was pointed out in the application that under normal operating conditions, that is, where the demand for cooling is relatively continuous, the in-ilow and out-how of heat are such as to produce pressures of the proper order of magnitude for circulating the coolant. However, it was explained that if a system of that type were operated for a sustained period under low ambient temperature conditions, it might stall upon the recurrence of a demand for cooling unless proper provision were made. This stalling would result from the reduction of the in-ilow of heat from the returned warm coolant, While the outow of heat to the Dry Ice bunder continued. Several structures and arrangements were accordingly suggested,

2,760,345 Patented Aug. 28, 1956 whereby the heat exchange relationship could be adjusted within certain limits as therein specied to prevent this condition from taking place. v

It is a principal object of the present invention to provide an improvement in the system to obtain increased control over the pressure in the generator. This control has as its object, not only the prevention of the abovementioned stailing, but also the prevention of the building up of excessive circulating pressures and excessive loss of Dry Ice. The cause of the latter might be a sustained high demand for cooling, which 4might result in an excessive in-ow of heat to the pressure generator from the returned warm coolant in the reservoir.

A further object is to provide a pressure-regulated system of the above type suitable for use with or without the improvement described in my above-mentioned Patent No. 2,608,832, whereby l provide a by-pass circuit for the coolant cooling tubes and a mixing valve for adjusting the proportion of cooled to uncooled coolant entering the space cooling tubes.

Still other objects are to provide appropriate safety devices and structural improvements for insuring the continuity of operation of the system and the preservation of the cargo in the space to be cooled.

With the above objects in View, a principal feature of the invention comprises a pressure regulating valve for separating the coolant tiowing from the reservoir into two paths, one path leading directly to the coolant cooling tubes as described in the various forms of the apparatus heretofore mentioned, and the other path leading to a pressure regulating heat exchanger beneath the Dry ice pressure generator. This heat exchanger, or double bottom is so arranged as to permit heat flow from the coolant to the Dry ice in the generator, and therefore may be used to increase or decrease its rate of sublimation. The pressure regulating valve provides means for diverting the entire flow to either of these paths, as well as for proportioning the iiow in any desired ratio, according to the pressure in the generator.

Another feature is the provision of a rupture disk in the pressure generator wall, whereby an absolute limit on the pressure is insured, regardless of freezing or plugging of any of the regulating valves or other devices.

Another feature is the use of an improved circulating coolant, such as ethylene glycol mono-ethyl ether or the equivalent, as hereinafter more fully described, whereby the safety and eiciency of the system are greatly improved.

Still another feature is the provision of a gas-tight lining completely separating the Dry ice containers from the space to be cooled. This lining prevents leakage of CO2 into the cargo so that the concentration of CO2 in the space to be cooled will not be greater than that in the outside atmosphere, or the increase in CO2 concentration in that space may be readily controlled by a valve in a tube connecting the Dry lce bunker therewith. Also, since CO2 gas is heavier than air and tends to move downward in the Dry lce bunker Iso as to draw in air at the top, a certain amount of snow resulting from condensation of moisture in the air tends to deposit ultimately upon the coolant cooling tubes, forming a bridging `of insulation which reduces the cooling effect of the Dry ice upon the coolant. The gas-tight lining prevents the continuous down-flow of gaseous CO2 in the Dry Ice bunker, and therefore greatly reduces the amount of air which can enter the bunker.

However, the above lining is vented to the outside through a cover and a vent at the top, as hereinafter described, so that CO2 pressure cannot build up therein.

Other features of the invention comprise certain devices, structures, and relationships of the parts hereinafter more fully described, and specifically defined in the claims.

In the drawings, Fig. l is a schematic diagram of a preferred embodiment of the invention; and

Fig. 2 is a detailed View of the pressure regulating valve.

Referring to Fig. l, I show in diagrammatic form a space cooling system according to the present invention. Systems of this type have been successfully operated in railroad cars and automotive trailers. The system may also be used, of course, in a stationary installation.

As heretofore mentioned, Dry Ice, preferably in the block form, is used for cooling the liquid coolant prior toits entry into the space cooling tubes. This Dry Ice is loaded through an opening at the top having a cover 2 into a Dry Ice bunker 3, which may be constructed as shown in my above-mentioned application, with a number of cooling tubes at the bottom, disposed in parallel fashion between headers connected into the coolant circulating system. An atmosphere vent 4 prevents the building up of pressure in the bunker.

The properties desirable in a coolant suitable for use in a system of this type include a high flash point and low viscosity at operating temperatures. The former property reduces the hazards inci-dent to the use of a combustible substance under extremes of ambient temperature and in the possible presence of sparks, as in a railroad installation. The latter property tends to eliminate sluggishness in the circulation. Accordingly, I preferably use one of the lower alkyl ethers of lower alkylene glycols, such as ethylene glycol mono-ethyl ether, commonly sold under the trade name Cellosolve, which I have found to be well suited to this application, not only in the above respects but in others pertinent to this type of cooling system.

Dry Ice for generating the circulating pressure, also preferably in the block form, is loaded into a Dry Ice pressure generator through an outside cover 5 and an opening having a gas-tight cover 6. The pressure generator may be constructed as shown in my above-mentioned copending application, except that it is provided with a second, or double bottom, which may be made of sheet metal welded to the sidewalls to provide a chamber through which the coolant may be circulated prior to its entry into the coolant cooling tubes. 'I'he heat exchanger may be provided with one or more partition walls, whereby the flow path is of any desired length, or the heat exchanger may be constructed in any other desired manner readily permitting the flow of heat from the coolant into the space above.

A rupture disk 8 is also preferably constructed into the wall of the pressure generator. This places an absolute limit on the pressure in the generator regardless of any failure of the valves or other parts of the circulating system, and in the preferred embodiment described I have found that a disk which ruptures at about 15 p. s. i. is normally quite satisfactory.

A pair of relief valves 10 connect the space above the sublimating CO2 in the pressure generator through a hand valve 12 to a main pressure line 14. The relief valves are provided with vents 15 and adjusted to hold the pressure in the line 14 at a substantially constant value above atmospheric, as explained in my above-mentioned application. They are connected in parallel to insure continuous application of pressure to the line 14 .in case one of them should become plugged with frost. The line 14 is connected with a pressure regulating valve, hereinafter to be more fully described, and with a coolant reservoir and iloat valve chamber, the latter being connected through a four-way valve 16. The valve 16, as well as the other parts of the float valve chamber and coolant reservoir are fully described in my above-mentioned copending application, but their operation will be briey summarized.

Warm brine returning from the space cooling tubes over a line 18 is vented into the iloat valve chamber. Within the chamber is .a oat 20 slideably mounted on a fixed spindle 22 having slots through which are projected a pair of lugs 24 and 26, secured to a valve stem 27. While the coolant rises in the chamber the valve stem 27 is in its down position, whereby an atmosphere vent 28 is connected with the space above the liquid in the chamber, and the pressure line 14 is disconnected from the chamber. In some instances the vent 28 may become plugged with frost. To avoid this possibility, it is preferably connected to the space above the Dry Ice in the bunker as shown in the drawing, since this space is at atmospheric pressure, but at a considerably reduced ternperature. It is also devoid of moisture by reason of the high concentration of CO2 gas caused by the gas-tight lining, hereinafter more fully described. At this time the pressure for circulating the coolant is provided by the connection of the line 14 with the space above the liquid in the coolant reservoir.

While the liquid is owing into the float valve chamber as above described, it is prevented from flowing downward through a pipe 30 into the coolant reservoir by reason of the pressure differential between the valve chamber and the coolant reservoir holding a check valve 32 closed. Also, liquid is prevented from ilowing in the reverse or upward direction through the pipe 30 by reason of the check valve.

Eventually, the float 20 reaches the lug 24 and moves the valve stem upward, thereby disconnecting the atmosphere vent 28 from the space above the valve chamber, and connecting the pressure line 14 therewith. This stops the circulation of brine through thesystem by removing the pressure differential previously existing between the line 14 and the line 18. Since the spaces above the liquid in the valve chamber and coolant reservoir are now at the same pressure, namely, that of the line 14, the liquid in the valve chamber ows by gravity through the pipe Si) into the coolant reservoir until the float 20 strikes the lug 26, thereby giving the valve stem a downward movement, and re-establishing the initial conditions.

Thus, except for the periods in which the liquid in the valve chamber is being removed into the coolant reservoir, a circulating pressure differential is continuously applied to the coolant, which ows through a line 34 to the pressure regulating valve.

The pressure regulating valve provides means for dividing the ilow from the pipe 34 between a line 36 and a line 38 according to the pressure in the line 14, which is connected to the valve by a line 40. Details of construction of the valve are shown in Fig. 2. A central body 42 has threaded extensions 44 and 46 to provide bearings for a spindle 48. Bellows sleeves 50 and 52 are threaded to the extensions 44 and 46, respectively, these sleeves being provided at their ends with means for clamping a pair of expansible metal bellows 54 and 56, respectively, in a well-known manner. Threaded fittings 58 and 60 are secured to the ends Vof the spindle 4S and to the movable ends of the bellows 54 and 56. The inside of the bellows 54 is connected with the atmosphere, while the 4inside of the bellows 56 is connected with the line 40. Thus, it will be seen that the position of the spindle 48 between a pair of shoulders 62 and 64 will depend upon the differential between atmospheric pressure, which will vary, for instance, with the altitude at which the system is moved, and the pressure in the line 40. However, as described above, the pressure in the line 40 is kept by the valves 10 at a substantially constant value above atmospheric, increasing or decreasing as the latter increases or decreases. Therefore, the position of the spindle, determining the division of the flow from the vline 34 between the lines 36 and 38, is substantially independent of atmospheric pressure.

The atmosphere bellows 54 is spring-compensated in a well-known manner to permit adjustment. An extension 66 threaded t-o the sleeve 50 has two slots running parallel to the axis of the spindle, into which are projected a .pair of pins 68. The pins are fitted into holes in a member '70, having threads engaging with an adjustment screw 72. By means of an adjustment lenob 74 pinned to the screw '712 it is possible to move the member 70 forward or back so as to increase or decrease the compression of a spring 75 tending to expand the bellows v54 by applying pressure to the fitting 58. It will also be noted that rupture of the bellows 56 causes the valve to lfail safe by reason of the spring 75 which moves the spindle 48 to divert the entire flow to the pressure regullating heat exchanger.

Thus, a certain amount of the coolant is directed from A.the pressure regulating valve to the line 38 and directly to the coolant cooling tubes, and the remaining coolant is directed through the line 36 to the pressure regulating heat exchanger, from which it passes through a check valve 76, which prevents any tendency to thermosyphonic back ow, and enters the coolant cooling tubes. Upon leaving the cooling tubes, the coolant passes through a line 78 to parrallel-connected space cooling tubes, preferably mounted at the ceiling above the space 'i9 to be cooled in the manner fuily shown :and described in my above-mentioned application and patent. Upon leaving the space cooling tubes the coolant may pass through one or more of three parallel-connected paths to the line 18, from which it is emptied into the float valve chamber. The above-described parallel connections are intended as safety measures against the plugging or failure of any part of apparatus in the space to be cooled. Hand valves provide means for isolating the parts of the apparatus most likely to fail during operation. These precautions have been dictated in part by the extremely high cost of cargo shipped under refrigeration in railroad car installations. A full discussion thereof is given in my above-mentioned copending application and patent. It will suffice to note, however, that the system is normally operated m'th a hand Valve 80 closed, so that the returning coolant must pass through one or both of two temperature-regualted valves 8l, compensated to eliminate the effect of pressure variations in the manner described in my above-mentioned application, which provide means for controlling the rate at which the returning brine iills the oat valve chamber. Thus, the temperature-regulated valves 81 provide means for regulating .the rate of repetition of the ow cycle.

In my above-mentioned application, it was recognized that certain heat exchange relationships exist between the Dry Ice pressure generator and the Dry Ice bun :er and coolant reservoir and related parts. According to the vpresent invention, I provide a pressure regualting heat exchanger in the floor of the pressure generator, and controlled means for diverting the ow of warm coolant into the exchanger to provide extremely close control over the net heat ow into the generator. This control is elected by the pressure in the main line 14 through the line 40 as described above. I also preferably provide insulation 82 as described in my above-mentioned application to reduce the out-dow of heat to the body of Dry Ice above the coolant cooling tubes, so as to effectively isolate the generator from this source of heat loss. Enough of the warm coolant passing through the line 34 is diverted to the heat exchanger to provide the necessary circulating pressure.

As disclosed in my above-mentioned patent No. 2,608,832, some cargoes, such as fresh vegetables, require that the temperature be held Within certain limits above the freezing point of water. For such loads, the temperature of the coolant passing through the line 3S may be too low. Accordingly, the above patent describes a system including a mixing valve to divert some of the coolant around the coolant cooling tubes, whereby the coolant entering the space cooling tubes comprises a mixture of the cooled and uncooled portions in any desired ratio. As shown in Fig. l, a line 84 is connected with ythe line 38 and with one input to the mixing valve. The coolant leaving the cooling tubes passes over a line 86 to the other input of the mixing valve. The line 78 is con# nected to the output of the mixing valve.

The presence of gaseous CO2 in the system affects the condition of the load and the operation of the system in at least two respects. First, it may escape into the space to be cooled and affect the cargo. While concentrations of CO2 in the atmosphere may be desirable for some loads, such `as fresh meats, it is undesirable for others, and in any event it is highly desirable to provide some means for controlling the concentration of the CO2 in the cargo space. Secondly, as heretofore indicated, since CO2 is heavier than air it tends to settle to the bottom of the apparatus, from which it leaks to the outside, thus drawing air into the system at the top of the apparatus. Moisture laden air entering the Dry Ice bunker in this fashion can cause considerable retardation in the eiciency of the system, since the moisture condenses as snow which blankets the cakes of Dry Ice and deposits directly upon the cooling tubes. This creates a form of heat insulation which is commonly experienced with ordinary household refrigerators, and which necessitates periodic defrosting.

Accordingly, I provide a gas tight lining 87 on the inside of the Walls of the Dry Ice bunker 3, :as shown in Fig. l. This lining is preferably made of sheet metal, such as aluminum, the pieces of which are preferably welded to each other, and welded or otherwise sealed to the tubes or vents leading to the outside. In this manner, I may exclude the CO2 gas generated in the apparatus from the space to be cooled. I may also permit a controiled quantity of the gas to escape to the cargo space 79 through a tube 88 and a hand-operated valve 9i). I also prevent the continuous ow of moisture-laden air into the bunker, and substantially eliminate the formation of snow on the coolant cooling tubes.

It should be noted that while the concentration of CO2 within the lining will be high, the pressure cannot build up by reason of the vent 4 leading to the outside at the top.

It will be understood that the invention has been described in relation to a preferred embodiment merely by way of illustration, and that various modifications as determined by the differing requirements and conditions of use will suggest themselves to one skilled in the art, and that such modiiications, or other .additions or changes may be made without departing from the spirit or scope of the invention.

Having thus described my invention, I claim:

1. A cooling system having the combination of a circulating system for a liquid coolant including a space cooling heat exchanger, a Dry Ice container having means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, intermittent circulating means for collecting the returned warm coolant and for circulating it through the space cooling heat exchanger, a pressure regulating heat exchanger adapted to transfer heat from the circulating Warm coolant into the generator, and a pressure-responsive valve for regulating the ow of coolant to said pressure regulating heat exchanger.

2. A cooling system having the combination of a circulating system for a liquid coolant including a space cooling heat exchanger, a Dry Ice container having means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, intermittent circulating means for collecting the returned warm coolant and for circulating it through the space cooling heat exchanger, a pressure regulating heat exchanger adapted to transfer heat from the circulating Warm coolant into the generator, and a valve responsive to the circulating pressure for regulating the iow to said pressure regulating heat exchanger.

3. A cooling system having the combination of a circulating system for at liquid coolant including a space cooling heat exchanger, a Dry Ice container having means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, a coolant reservoir, a float valve chamber supported above the reservoir adapted for receiving the returned warm coolant and provided with means for intermittently filling the reservoir with coolant and for causing circulation from the reservoir to the space cooling heat exchanger, a pressure regulating heat exchanger connected with the reservoir and adapted to transfer heat from the circulating warm coolant into the generator, and a pressure-responsive valve for regulating the flow of coolant to said pressure regulating heat exchanger.

4. A cooling system having the combination of a circulating system for a liquid coolant including a space cooling heat exchanger, a Dry Ice container having means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, a coolant reservoir, a oat valve chamber supported above the reservoir adapted for receiving the returned Warm coolant and provided with means for intermittently lling the reservoir with coolant and for causing circulation from the reservoir to the space cooling heat exchanger, a pressure regulating heat exchanger connected with the reservoir and adapted to transfer heat from the circulating warm coolant into the generator, and a valve responsive to the circulating pressure for regulating the ow to said pressure regulating heat exchanger.

5. A cooling system having the combination of a circulating system for a liquid coolant including a space cooling heat exchanger, a Dry Ice container having means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, a coolant reservoir, a float valve chamber supported above the reservoir adapted to receiving the returned warm coolant and provided with means for intermittently lling the reservoir with coolant and for causing circulation from the reservoir to the space cooling heat exchanger, a pressure regulating heat exchanger connected with the reservoir and adapted to transfer heat from the circulating warm coolant into the generator, a valve responsive to the circulating pressure for regulating the ow to said pressure regulating heat exchanger, and a by-pass for the pressure regulating heat exchanger controlled by said valve.

6. A cooling system having the combination of a cirthe generator, a heat exchanger adjacent to said Dry Ice 'container to receive coolant from the pressure regulating heat exchanger land to deliver it to the space `cooling heat exchanger, and prsure sensitive valve means including a by-pass for the pressure regulating heat exchanger for regulating the flow of coolant therethrough.

7. A cooling system having the combination of `a circulating system for a liquid coolant, including a space cooling heat exchanger, a Dry Ice container having means toV cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, intermittent circulating means for collecting the returned warm coolant and forV circulating it through the space cooling heat exhanger, heat insulation separating the generator from the Dry Ice container, a pressure regulating heat exchanger adapted to carry a controlled fraction of the returned warm coolant into heat exchanger relationship with the generator, and a pressure-responsive valve for regulating the oow of coolant to said pressure regulating heat exchanger.

8. A cooling system having, in combination, a circulating system fora liquid coolant including a space cooling heat exchanger, means to cool the coolant, a generator to hold a supply of Dry Ice for applying circulating pressure to the coolant, circulating means operative by applying said pressure to the coolant to circulat it throughsaid system, a pressure regulating heat exchanger connected with said system and adapted to transfer heat from the returned war-m coolant to the generator, and a valve responsive to said pressure for regulating the flow of coolant to said pressure regulating heat exchanger.

9. A cooling system having, in combination, a circulating system for a liquid coolant including a space cooling heat exchanger, a container to hold a supply of Dry Ice for generating a pressure, circulating means operative by applying said pressure to the coolant to circulate it through said system, a pressure regulating heat exchanger and a by-pass line connected in parallel with the pressure regulating heat exchanger in said system, said pressure regulating heat exchanger being adapted to transfer heat from the coolant to said container, and a valve to proportion the liow of coolant between said pressure regulating heat exchanger and said by-pass line as a function of said pressure, whereby a decrease in the pressure produces an increase in the proportion of coolant circulated through said pressure regulating heat exchanger.

References Cited in the le of this patent UNITED STATES PATENTS 1,510,759 Buch Oct. 7, 1924 1,892,741 Sorensen Jan. 3, 1933 1,943,315 Hulse Jan. 16, 1934 2,097,685 Bolton Nov. 2, 1937 2,187,388 Williams Jan. 16, 1940 2,380,537 McMechan Iuly 31, 1945 2,450,713 Brunsing Oct. 5, 1948 2,507,866 Plesset et al May 16, 1950 2,608,832 Woods Sept. 2, 1952 2,636,357 Woods Apr. 28, 1953 FOREIGN PATENTS 108,440 Australia Sept. 14, 1939 406,974 Great Britain Nov. l-l, 1933 

